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Maybe ‘bird brain’ isn’t such an insult after all – the latest research has found that ravens, the ubiquitous city bird, can count out loud to four.
Not only can the inquisitive creatures count, but they can also match the number of calls they make when shown a number, according to a new study led by a team of researchers from the Animal Physiology Laboratory of the University of Tübingen in Germany.
The way birds recognize and respond to numbers is similar to a process we humans use both to learn to count as young children and to quickly recognize how many objects we are looking at. The findings, published Thursday in the journal Science, add to our growing understanding of ravens’ intelligence.
“Humans do not have a monopoly on skills such as digital thinking, abstraction, tool making and forward planning,” animal cognition expert Heather Williams said by email. “No one should be surprised that ravens are ‘smart.'” Williams, a professor of biology at Williams College in Massachusetts, was not involved in the study.
In the animal kingdom, counting is not limited to ravens. Chimpanzees are taught to count in numerical order and to understand the value of numbers, much like young children. In their attempts to court mates, some male frogs count the number of calls from competing males to match or even increase that number when it is their turn to croak at a female. Scientists have even theorized that ants find their way back to their colonies by counting their steps, although the method is not always accurate.
What the latest study showed is that ravens, like young people, can learn to associate numbers with values – and count aloud accordingly.
The study was inspired by young children learning to count, said lead study author Diana Liao, a neurobiologist and senior researcher at the Tübingen lab. Young children use number words to count the number of objects in front of them: If they see three toys in front of them, their counting may sound like “one, two, three” or “one, one, one.”
Perhaps the ravens could do the same, Liao thought. She was also inspired by a June 2005 study on chicks adjusting their alarm signals to the size of a predator. The larger the predator’s wingspan or body length, the fewer “dee” sounds the chicks use in their alarm signal, the study found. The opposite was true for smaller predators — songbirds would use more “dee” sounds if they encountered a smaller bird, which could be more of a threat to chickens because they are more agile, Liao said.
The authors of the chicken study could not confirm whether the baby songbirds had control over the number of sounds they made, or whether the number of sounds was an involuntary response. But the possibility piqued Liao’s curiosity—could ravens, whose intelligence has been well-documented over decades of research, show control over their ability to produce a set number of sounds, effectively “counting” like toddlers?
Liao and her colleagues trained three crows, a European species closely related to the American crow, over more than 160 sessions. During training, the birds had to learn associations between a series of visual and auditory cues from 1 to 4 and produce the corresponding number of calls. In the example provided by the researchers, a visual cue might look like a bright blue number, and its corresponding sound might be a half-second drum track.
The ravens were expected to produce the same number of caws as the number represented by the cue—three caws for the number 3 cue—within 10 s of seeing and hearing the cue. When the birds stopped counting and squawking, they would peck the “enter” key on the touch screen that displayed their cues to confirm they were ready. If the birds counted correctly, they would get a treat.
It appears that as the cues continue, the ravens take longer to respond to each cue. Their reaction times increased as “more vocalizations were forthcoming,” Liao wrote, suggesting that the ravens planned the number of caws they would make before opening their beaks.
The researchers could even tell how many calls the birds planned to make by the way their first call sounded—subtle acoustic differences that showed the ravens knew how many numbers they were looking at and had synthesized the information.
“They understand abstract numbers … and then plan ahead as they match their behavior to match that number,” Williams said.
Even the mistakes made by the ravens were somewhat advanced: If the ravens cawed too many times, stuttered over the same number, or transmitted their answers with their beaks prematurely, Liao and her researchers could tell from the sound of the first call where they had gone. wrong. These are “the same kinds of mistakes that people make,” Williams said.
Birds and many other animals were previously thought to make only on-the-spot decisions based on stimuli in their immediate environment, a theory popularized by 20th-century animal behaviorist B.F. Skinner. But the latest research by Liao and her colleagues provides more evidence for ravens’ ability to synthesize numbers to produce sound, and suggests that this skill is under their control.
The research team’s findings are very specific but still significant — they challenge the once-held belief that all animals are simply stimulus-responsive machines, said Kevin McGowan, a researcher at the Cornell Lab of Ornithology in Ithaca, N.Y., who has spent more more than two decades of studying wild crows in their habitats. McGowan was not involved in the study.
The study, McGowan told CNN, demonstrated that “crows are not just simple unthinking machines that respond to their environment — they actually think ahead and have the ability to communicate in a structured, pre-planned way.” It is something of a necessary precursor to the existence of language.
The intelligence of ravens has been studied for decades. Scientists have studied New Caledonian crows creating their own composite tools to access food. Birds seem to establish rules, according to a November 2013 study co-authored by Tübingen University Laboratory lead researcher Andreas Nieder. Crows’ language has also baffled scientists for decades with its wide variety of tones and expressions, McGowan said.
The study by Liao and her colleagues isn’t even the first to look at whether ravens can count. This research began with Nicholas Thompson in 1968, notes animal cognition expert Irene Pepperberg. A research professor of psychology and brain sciences at Boston University, Pepperberg is best known for her work with an African gray parrot named Alex.
Thompson hypothesized that ravens can count based on their cawing, the duration and number of which the birds seem to control in a given burst of sound. Ravens’ counting abilities “seem to exceed the demands that survival places on such abilities,” he wrote.
Another University of Tübingen study on ravens’ counting abilities from September 2015 trained the birds to recognize groups of dots and recorded the activity of neurons in the part of the ravens’ brains that receives and makes sense of visual stimuli. The researchers found that the ravens’ neurons “ignore the size, shape, and location of the dots and extract only their number,” the university said in a statement at the time.
“So ravens’ brains can represent different quantities, and ravens can quickly learn to associate Arabic numerals with those quantities—something that humans usually explicitly teach their children,” Williams said.
